KR100469082B1 - A hydrophilic polyurethane foam for wastewater treating - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to hydrophilic polyurethane foams for wastewater treatment, and more particularly, to a porous polyurethane foam prepared mainly from a polyol compound and a diisocyanate compound, wherein the polyalkylene oxide contains polyethylene oxide as an auxiliary surfactant. By adding an appropriate amount of modified polydimethyl siloxane to foaming reaction, the hydrophilicity of the polyurethane foam is improved by hydrophilic groups oriented on the surface of the polyurethane foam, and when applied as a fluidized bed carrier for wastewater treatment, it settles upon initial introduction into the wastewater treatment plant. The present invention relates to a hydrophilic polyurethane foam for wastewater treatment, which can reduce the operating time of a wastewater treatment plant by increasing the speed, and increase the affinity with microorganisms and organic substances having strong hydrophilicity to enable efficient wastewater treatment.

Description

A hydrophilic polyurethane foam for wastewater treating

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to hydrophilic polyurethane foams for wastewater treatment, and more particularly, to a porous polyurethane foam prepared mainly from a polyol compound and a diisocyanate compound, wherein the polyalkylene oxide contains polyethylene oxide as an auxiliary surfactant. By adding an appropriate amount of modified polydimethyl siloxane to foaming reaction, the hydrophilicity of the polyurethane foam is improved by hydrophilic groups oriented on the surface of the polyurethane foam, and when applied as a fluidized bed carrier for wastewater treatment, it settles upon initial introduction into the wastewater treatment plant. The present invention relates to a hydrophilic polyurethane foam for wastewater treatment, which can reduce the operating time of a wastewater treatment plant by increasing the speed, and increase the affinity with microorganisms and organic substances having strong hydrophilicity to enable efficient wastewater treatment.

Recently, the seriousness of environmental pollution is increasing as a social problem, and in Korea, more than half of the appeals are already eutrophicated or in progress due to side effects from rapid industrialization. To date, more than 90% of domestic wastewater purification methods have applied activated sludge method, which is a method using only floating microorganisms, which is not easy to maintain and generates a large amount of excess sludge and excessive amount of site. In addition, there is a problem in that the fluid retention time and the sludge residence time must be separated and operated while maintaining a high concentration of microorganisms in the aeration tank for efficient operation. Therefore, in advanced countries such as Europe, researches on the biofilm process applying the concept of biofilm have been actively conducted as an alternative to solve the above problems since the 80s, and a large portion of the applied sludge method has already been applied.

Biofilm treatment process is basically a method that uses the ability of microorganisms to purify the microorganisms are attached to the medium, that is, a carrier is required, the wastewater treatment efficiency is greatly different depending on the type of carrier used and the filling method. That is, the basic properties such as the material, chemical properties, size, shape, surface area, and porosity of the carrier used in the biofilm treatment process are the biggest factors that determine the treatment performance of the wastewater. Up to now, the carrier material has been mainly used in natural stone such as crushed stone, and recently, inorganic particles such as ceramics and activated carbon, fibers and synthetic plastics are used. Since only research efforts have been made to increase specific surface area and porosity for the purpose of providing attachment points, no efforts have been made to understand and apply the characteristics of microorganisms. In other words, most of the materials used up to now have strong hydrophobic materials. Especially, synthetic plastics such as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) have mostly negative surface charges in the neutral region. Because of its poor affinity with microorganisms having strong hydrophilicity, it takes several months for the microbial membrane to be formed after being applied to the actual wastewater treatment to show the decomposition effect of organic matter. However, recent studies have shown that the formation of microbial membranes not only affects the physical aspects but also the electrical and chemical properties of surface charge, hydrophilicity, etc., have a significant effect on the initial deposition rate of microorganisms.

Therefore, in recent years at home and abroad, the manufacturing method and the porosity control, easy to control and excellent durability, and has a polar segment (segment) structure in the basic structure, the microbial adhesion properties compared to other materials polyurethane foam form Carriers have been developed, and in Korea, such carriers have already been developed around environmental engineering companies, and have been partially applied to domestic wastewater treatment plants and sewage treatment plants.

However, the polyurethane foam carrier, which has been developed and applied up to now, has a very low hydrophilization performance, and when it is introduced into an initial water treatment plant, it takes a considerable time for the actual carrier to be immersed in water and flowable. Some of the urethane foam carriers are suspended without being completely immersed, which serves to reduce the treatment efficiency of the wastewater. As part of efforts to solve the above problems, there are attempts to improve the hydrophilization performance by introducing raw materials having hydrophilic groups and hydrophilic additives, but most hydrophilic raw materials are sensitive to moisture, which adversely affects storage stability and foaming reaction. In addition, the method of coating and impregnating hydrophilic components after foaming is also attempted, but the manufacturing process is difficult and mass production is difficult, and most raw materials used are expensive, causing cost increase, and the strength and wear resistance of the manufactured polyurethane foam. Problems such as deterioration of physical properties, etc. remain a problem to be solved.

Accordingly, the inventors of the present invention have made efforts to solve the above problems, and when the polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide is added as an auxiliary surfactant in an appropriate amount to foam the reaction, the surface of the polyurethane foam Hydrophilic group is oriented to improve the hydrophilicity of polyurethane foam, and it speeds up the sedimentation rate during initial input into the wastewater treatment plant to shorten the operating time of the wastewater treatment plant and increases the affinity with the hydrophilic microorganisms and organic matters for efficient wastewater treatment It was found that the possible to complete the present invention.

Therefore, an object of the present invention is to provide a porous polyurethane foam for wastewater treatment with improved hydrophilicity which can be applied as a fluidized bed carrier for wastewater treatment.

The present invention is a porous polyurethane foam prepared by using a polyol compound and a diisocyanate compound as a main component and foaming reaction thereof, and is modified with a polyalkylene oxide containing polyethylene oxide based on 100 parts by weight of the polyol compound, Characterized by hydrophilic polyurethane foam for waste water treatment prepared by the foaming reaction including 0.2 to 2.0 parts by weight of polydimethyl siloxane represented by 2. Where PE ₁ is —CH ₂ CH ₂ CH ₂ O (EO) _m (PO) _n R, where PE ₂ is — (EO) _m (PO) _n R ′, Me is a methyl group, EO is ethylene oxide Group, PO is a propylene oxide group, R, and R 'respectively represents a C1-C6 alkyl group, m is 5-100, n is 0-100, p is 3-50, q is 3-5, x is 1-50 and y are 1-5.

The hydrophilic polyurethane foam for wastewater treatment of the present invention is a polyol compound, a polyol such as polypropylene glycol (hereinafter referred to as "PPG"), which is relatively inexpensive, an aromatic diisocyanate compound, a silicone surfactant for obtaining a stable foam, a tin catalyst, Additives such as amine catalysts and water are reacted together, and polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide is added as an auxiliary surfactant to impart hydrophilicity thereto. It is useful as a fluidized bed microbial carrier for water treatment by maximizing hydration performance.

The present invention will be described in more detail as follows.

The polyurethane foams of the invention feature polydimethyl siloxanes modified with polyalkylene oxides containing polyethylene oxide as auxiliary surfactant.

0.2 to 2.0 parts by weight of polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide is used with respect to 100 parts by weight of the polyol compound, and when the amount is less than 0.2 parts by weight, sufficient hydrophilicity cannot be exhibited, and it is more than 2.0 parts by weight. The lower surface strength and the reduction of interfacial energy caused by dimethylsiloxane cause shrinkage.

Preferably, the polydimethylsiloxane has a molecular weight in the range of 500 to 5000. In this case, when the molecular weight is less than 500, the solubility in water is increased to decrease hydrophilicity when reused, and when the molecular weight exceeds 5000, the content of dimethylsiloxane is relatively increased. Its hydrophilicity decreases and shrinkage occurs. The content of polyethylene oxide contained in the modified polydimethyl siloxane is preferably 25 to 75% by weight of the total, wherein when the content of polyethylene oxide is less than 25% by weight, sufficient hydrophilicity cannot be imparted and other additives exceeding 75% by weight. The tendency of the compatibility with the oil tends to be lowered, so that it is not possible to form a stable bubble.

Polyalkylene oxides that may be used to modify the polydimethyl siloxane include polyethylene oxide, polypropylene oxide, and the like, and at least one polyethylene oxide may be included in the structure. That is, the surfactants modified with polyalkylene oxide are largely all added with only ethylene oxide (EO), both with ethylene oxide (EO) and propylene oxide (PO) added, and all of propylene oxide (PO). It can be classified into three types of added form, and the higher the content of ethylene oxide than the content of propylene oxide, the better the hydrophilization performance.

The polydimethylsiloxane modified with polyalkylene oxide as described above represents the form of a block copolymer type, and can be broadly classified into the following two classes.

The first is a polydimethylsiloxane having a linear structure in which the polyalkylene oxide is a side chain, and may be represented by the following Chemical Formula 1.

[Formula 1 [

Wherein PE ₁ is —CH ₂ CH ₂ CH ₂ O (EO) _m (PO) _n R, Me is a methyl group, EO is an ethylene oxide group, PO is a propylene oxide group, R is an alkyl group having 1 to 6 carbon atoms, m is 5-100, n is 0-100, x is 1-50, y is 1-5.

Second, the polyalkylene oxide group is located at the end of the silicon backbone to form a Si-O-C bond, which can be represented by the following formula (2).

[Formula 2]

Where PE ₂ is-(EO) _m (PO) _n R ', Me is a methyl group, EO is an ethylene oxide group, PO is a propylene oxide group, R' represents an alkyl group having 1 to 6 carbon atoms, and m is 5 to 100, n is 0-100, p is 3-50, q is 3-5.

When polydimethyl siloxane modified with a polyalkylene oxide containing polyethylene oxide as described above is used as an auxiliary surfactant, the hydrophilicity and wetting ability of the polydimethyl siloxane are higher than those of the conventional silicone-based surfactant. The surface of the polyurethane foam can be modified from hydrophobic to hydrophilic. In addition, when the polydimethyl siloxane modified with the polyalkylene oxide of the present invention having the above structure is used as an auxiliary surfactant, it has good compatibility with the unmodified dimethyl siloxane used in the manufacture of foam. Even when used simultaneously, it is sufficient to obtain a stable foam shape.

Referring to the manufacturing process of the hydrophilic polyurethane foam according to the present invention in more detail.

The first step is to add a silicone foam stabilizer, tin catalyst, amine catalyst and water to the polyol compound, and polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide, which is characteristically included in the present invention, as an auxiliary surfactant. It is a process of dispersion and stirring at about 1000 ~ 1500 rpm at room temperature. As the polyol used to exhibit moderate strength and elongation, polypropylene glycols having a molecular weight in the range of 3000 to 7000 are suitable, and more preferably in the range of 5000 to 6000. The silicon foam stabilizer is used to control the formation of stable cells and the openness and air permeability of the cell membrane, but it is preferable to use 0.4 to 0.8 parts by weight based on 100 parts by weight of the polyol compound. Tin catalyst is a component added to promote resination reaction in the reaction between diisocyanate and polyol, and 0.2 to 0.5 parts by weight is suitable for 100 parts by weight of polyol, and amine catalyst is added to promote blowing reaction. It is preferable to use 0.25-0.4 weight part with respect to 100 weight part of polyols as a component to become. Water has a great influence on the density of the foamed polyurethane foam as a blowing agent, and in order to adjust the density of the polyurethane foam prepared in the present invention to 40 ± 5 kg / m ³ 1.5 to 2.5 parts by weight based on 100 parts by weight of polyol It is suitable to use. Polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide is used to impart hydrophilicity performance to the foam, and should be compatible with the silicone foam stabilizer used above, with respect to 100 parts by weight of the polyol compound It is preferable to use 0.2 to 2.0 parts by weight, and its content can be adjusted according to the degree of demand for hydrophilization performance.

The second process is a process of preparing a porous polyurethane foam by mixing and then foaming aromatic diisocyanate in the polyol and additive mixture.

Aromatic diisocyanate is generally used in the production of polyurethane, all can be used, it is preferable to use toluene diisocyanate (hereinafter referred to as "TDI") that is easy for mass production of the continuous slab method. The aromatic diisocyanate compound is added in an amount of 30 to 40 parts by weight based on 100 parts by weight of the polyol mixture, and the ratio of the hydroxyl group (-OH) and the isocyanate group (-NCO) is in the range of 0.95 to 1.20, using 3000 to 6000 rpm. Prepared by stirring.

Polyurethane foam that can be produced by the above method is a porous poly after going through a membrane treatment process using an explosive gas, which is a post-treatment process used in the manufacture of a general porous polyurethane foam (filter foam) to secure porosity (porosity) Made of urethane foam.

Polyurethane foam as described above possesses the basic abrasion resistance, strength and porosity required as a fluidized bed carrier and is endowed with hydrophilicity so that it can be settled quickly in the water treatment plant for a start-up time. As well as reducing the affinity with the microorganisms and organic matter in the water can lead to rapid microbial growth can be very useful as a microbial carrier for biological treatment of wastewater and sewage.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Examples 1-8 and Comparative Examples

The polyol mixture was introduced into a mixed stirring vessel at 20 to 25 ° C., and a silicon foam stabilizer, tin catalyst, amine catalyst and water were added as shown in Table 1, followed by polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide. Was added to the auxiliary surfactant and stirred, and then diisocyanate was added and stirred at 3000 to 6000 rpm to foam and then membrane treated to prepare a porous polyurethane foam having a porosity of 95% or more.

Experimental Example: Comparison of Hydrophilicity Performance

<Sedimentation Speed>

After cutting the polyurethane foam specimen to a size of about 12 × 12 × 12 mm and dropping it at a certain height (10 cm) in a 250 ml beaker containing about 25 ° distilled water until the foam is completely submerged in water. The average time of was measured.

<Absorbance>

Take the prepared polyurethane foam to the size of 3 × 3 × 1 ㎝ to measure the initial weight (A), and impregnated and stored in 25 ℃ distilled water for 24 hours, and then take out the surface with a dust-free tissue to remove the weight (B ) Is calculated using the following equation.

Absorbance (%) = (B-A) / A × 100

As shown in Table 2, when the polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide is added to the auxiliary surfactant, the sedimentation rate is remarkably fast in proportion to the input content, and even a small amount is added. The effect can be obtained. In addition, the results of the comparison of the absorbency also shows that the absorbance increases in proportion to the input content, and in the case of the comparative example in which the polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide was not added, the reference time was 24 hours. It can be seen that the absorbency is considerably low even after the evaporation of the foam.

As described above, when polydimethyl siloxane modified with polyalkylene oxide containing polyethylene oxide is added as an auxiliary surfactant, the hydrophobicity is improved and the polyurethane foam itself is hydrophilized, and even with a small amount of hydrophilicity, It is possible to induce cost reduction, and it has good compatibility with the additives used for the article, and it does not have a big influence on the reactivity. When used as a preferred effect can be obtained.

That is, it is the most ideal microbial carrier for microbial habitat by greatly improving hydrophilization performance in addition to basic characteristics such as specific surface area, porosity and variety of cell size and ease of specific gravity control of polyurethane foam carrier. It can be applied, and it is possible to give high hydrophilic performance without any problem on reactivity, physical properties and productivity in producing polyurethane foam having excellent strength and abrasion resistance required as a fluidized bed microbial carrier. In addition, by maximizing the affinity with the microorganisms with strong hydrophilicity, there is an effect of shortening the start-up time, which is a problem of the conventional carrier, and maximizing water treatment efficiency.

Claims (4)

In the porous polyurethane foam prepared by using a polyol compound and a diisocyanate compound as a main component and foaming reaction, For 100 parts by weight of the polyol compound, it is modified by a polyalkylene oxide containing polyethylene oxide and then produced by foaming reaction containing 0.2 to 2.0 parts by weight of polydimethyl siloxane represented by the formula (1) or 2 for wastewater treatment Hydrophilic polyurethane foams; [Formula 1] [Formula 2] Where PE ₁ is —CH ₂ CH ₂ CH ₂ O (EO) _m (PO) _n R, where PE ₂ is — (EO) _m (PO) _n R ′, Me is a methyl group, EO is ethylene oxide Group, PO is a propylene oxide group, R, and R 'respectively represents a C1-C6 alkyl group, m is 5-100, n is 0-100, p is 3-50, q is 3-5, x is 1-50 and y are 1-5. The hydrophilic polyurethane foam for waste water treatment according to claim 1, wherein the modified polydimethyl siloxane has a molecular weight in the range of 500 to 5000. 2. The hydrophilic polyurethane foam for wastewater treatment according to claim 1, wherein the modified polydimethyl siloxane comprises 25 to 75 wt% of polyethylene oxide. delete